It's likely that you should. What are you buying? You'd be surprised how many of the 'new and popular' books the library keeps on hand these days. Especially the ones that find their way on the popular 'top 100 lists.' You know the ones.
Additionally, many public libraries have digital loan programs that allow you to use the books on your E-devices. For free, as usual. Even buying on itunes or kindle seems cheaper than B&N these days.

If it was some specialty book that you'd like to keep, then I guess a hard copy is fine. But you'd be better off shopping at amazon, or half.com.
I honestly have no idea how big box book stores are still in business

it would all depend on 1: what was in stock, 2: what my needs were, 3: what i feel like reading at that point in time.

I usually check through the Science Fiction/Fantasy/Horror section. The teen/8-12 section for favourites from when I was a kid, or newer books that are well written like Rick Riordan/Hunter Games. The humours section (Scott Adams Dilbert/Steven Colbert etc), the philosophy/religion section, etc. Check through all the on sale bins for books i figure I ought to read (like Don Quixote). A brief look through the poetry books, etc.

I have an entire room in my apartment dedicated as storage.. and it is mostly books.

The Design of Everyday Things? I am guessing that its Non-Fiction, what sort of theory was it espousing? How far back, and how detailed is your book about the profession of nursing?

You sound like you are excited about going for grad school, so good on you. What do you plan on doing with it?

If you are at all interested in Religion (either as an atheist or religious) have you ever tried 'Misquoting Jesus'? or really anything by Ehrman. Or if you are interested in biology at all, I found Richard Dawkins books rather well written.